The present invention relates generally to a method and an apparatus for the generation of elevator car position information and, in particular, to the formation of signals for actuating the door mechanisms of a stopping elevator car.
The prevention of a premature initiation of the door opening during the leveling operation of an elevator car into a destination floor places high technological demands on the devices and circuits which bridge or enable the door and lock contacts at the stop within a door zone during the leveling operation. There exist safety regulation provisions and standards which prescribe and recommend the principle of operation and the main functions of such devices and circuits. Assemblies of such devices and circuit, which comply with these respective safety regulations, are known by the term "fail-safe" assembly.
Such an assembly is described as a fail-safe detector in U.S. Pat. 3,743,056. The detector shown in this patent is a photoelectric reflective system. Appropriately positioned reflective plates or vanes in the elevator shaft reflect a pulsed infrared signal to a light receiver such as a phototransistor which generates a pulsed output signal which is tested for its authenticity by comparison of its amplitude with a reference value. The light receiver output signal must correspond in frequency to the light emitter signal whereby outside light reflections become ineffective. Furthermore, the circuit components are chosen and designed in such a manner, that the breakdown of individual or several components would not result in any safety endangering switching function.
The above described device has the disadvantages of the lack of a backup or auxiliary circuit in the case of a failure and that the various switching circuits are arranged in a decentralized manner.